Several years ago, while I was working for Toysrus.com I created an In-Memory database of their inventory items using ColdFusion. There were about 30,000 parts and ColdFusion was easily able to handle that much memory in their structures. The time-consuming ascept of that project was developing the code to read the information from the database into memory. Today, in Java world, Object Prevalance, makes the same task much easier.
The home page for the Object Prevalence system that I use is http://www.prevayler.org/wiki.jsp?topic=StartingPoints. I won't spend any time describing the concepts, but you can read about them there. I first started looking at Object Persistence technologies because I wanted to write a JarSearcher application. I could search the store for any class. Frequently when I'm compiling someone else's code, I find class references that I'm unfamilar with and don't know which Jar file the class is in. My JarSearcher would pre-search Jar files so that I could quickly find the class that I need. The application works in two steps. First, .jar files are indexed. And then class names are found as needed. You'll find my source code at JarSearcher.zip. The docomentation is rather sparse for now. The js.bat file shows how to invoke the application. The java_projects.txt file shows how to create a script for the application to follow. Please send comments to myself at email@example.com. After you send email, you'll be asked to verify that you're human (instead of a spammer) by SpamArrest.